This invention relates to load cells and method of manufacturing the same.
A load cell has a plurality of resistors formed on strain generating sections of a beam body, and a load applied to the beam body is measured by making use of the fact that the resistance of the resistor is changed according to the strain generated in the strain generating section at the time of the application of the load to the beam body. Hitherto, it has been a practice to form a load cell by bonding a metal foil of constantan, Nichrome, etc. to an insulating film of each material as polyimide or epoxy resin, appropriately etching the metal foil to form a resistor pattern to thereby form a load cell element and bonding the load cell element thus formed to the strain generating section of the beam body. This prior art method of manufacture of a load cell, however, requires a number of steps. Particularly, the step of bonding the load cell element to the beam body requires strict process control, and also its automation and mass production scale operation are difficult, thus giving rise to high cost. In addition, there is a lower limit of the thickness of the insulating film that can be obtained, so that it is difficult to permit strain generated in the strain generating section of the beam body to be transmitted with high efficiency to the resistors, thus leading to measurement errors. Further, while the resistor pattern is formed by the metal foil, it is difficult to form the metal foil sufficiently thin and obtain resistors having a high resistance. Consequently, high power is consumed at the time of the measurement, and this high power consumption is accompanied by high heat generation at the time of the measurement so that temperature compensation is called for.